Cancer is presently the second leading cause of death in developed nations. Wingo et al., J. Reg. Management, 25:43-51 (1998). Despite recent research that has revealed many of the molecular mechanisms of tumorigenesis, few new treatments have achieved widespread clinical success in treating solid tumors. Current treatments for most malignancies thus remain gross resection, chemotherapy, and radiotherapy. While increasingly successful, each of these treatments still causes numerous undesired side effects. The primary cause of these side effects is that none of these conventional methods specifically targets only diseased cells. For example, surgery results in pain, traumatic injury to healthy tissue, and scarring. Radiotherapy and chemotherapy cause nausea, immune suppression, gastric ulceration and secondary tumorigenesis.
In an effort to develop techniques to more specifically target diseased cells, progress in tumor immunology has led to the discovery of antigens that are preferentially or specifically expressed by cancer cells. The identification of tumor-specific cellular markers has proven extremely valuable for diagnosing and assessing the progression of certain types of tumors. Antibodies specific for tumor cell markers or ligands that bind specifically to a tumor cell receptor have been successfully used in diagnostics, including both the characterization of excised tissue samples and in vivo imaging. Tumor-specific antibodies and ligands have also been used in the targeted delivery of cytotoxic molecules to specific tumor cells. Some tumor cell antigens are known to function in the pathogenesis of a cancer. Modulating the function of these antigens could impair the progression of the disease.